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United States Patent |
5,139,587
|
Strecker
,   et al.
|
August 18, 1992
|
Composite solid propellant with a pulverulent metal/oxidizer agglomerate
base
Abstract
A composite solid propellant with a stable burning rate comprising ammonium
perchlorate, a binder system of telomeric polybutadiene or copolymers of
butadiene and acrylonitrile with terminal functional groups or functional
groups distributed statistically along the chain, which are hardened by
means of corresponding hardeners into rubber-elastic binders, finely
pulverized, readily oxidizable metals and, optionally, inorganic
fluorides, plasticizers and burning rate moderators, wherein ammonium
perchlorate together with one or more of said finely pulverized metals, as
well as, optionally, said inorganic fluorides are present as an
agglomerate of larger particles having a particle size of between 100
.mu.m and 2,000 .mu.m.
Inventors:
|
Strecker; Rudiger (Waldkraiburg, DE);
Harrer; Alois (Waldkraiburg, DE)
|
Assignee:
|
Bayern-Chemie GmbH (Aschau, DE)
|
Appl. No.:
|
040395 |
Filed:
|
May 10, 1979 |
Foreign Application Priority Data
Current U.S. Class: |
149/19.9; 60/207; 149/19.2; 149/22; 149/76; 149/119 |
Intern'l Class: |
C06B 045/10 |
Field of Search: |
60/207,208
149/192.,19.9,22,119,76,20
|
References Cited
U.S. Patent Documents
3068641 | Dec., 1962 | Fox | 60/207.
|
3476622 | Nov., 1969 | Harada et al. | 149/19.
|
3646174 | Feb., 1972 | Macvi | 149/22.
|
3753811 | Aug., 1973 | Julian et al. | 149/22.
|
3761330 | Sep., 1973 | Lou et al. | 149/19.
|
3873385 | Mar., 1975 | Henrich et al. | 149/19.
|
3986909 | Oct., 1976 | Macvi | 149/19.
|
4000024 | Dec., 1976 | Roberto et al. | 149/19.
|
4133173 | Jan., 1979 | Schadow | 60/207.
|
4141768 | Feb., 1979 | Lo et al. | 149/19.
|
Other References
Hawley, "The Condensed Chemical Dictionary", 9th Ed., p. 210, Van Nostrand
Reinhold Co. (1977) New York.
|
Primary Examiner: Miller; Edward A.
Attorney, Agent or Firm: Felfe & Lynch
Claims
We claim:
1. A composite solid propellant with a stable burning rate comprising
ammonium perchlorate; a binder system of telomeric polybutadiene or
copolymers of butadiene and acrylonitrile with terminal functional groups
or functional groups distributed statistically along the chain, which are
hardened by means of corresponding hardeners into rubber-elastic binders;
finely pulverized, readily oxidizable metals and, optionally, inorganic
fluorides, plasticizers and burning rate moderators, wherein ammonium
perchlorate together with one or more of said finely pulverized metals, as
well as, optionally, said inorganic fluorides are present as an
agglomerate of larger particles having a particle size of between 100
.mu.m and 2,000 .mu.m, said agglomerate consists of 19% to 61% by weight
of ammonium perchlorate with an average particle size of 0.4 .mu.m to 10
.mu.m; 38% to 75% by weight of boron with a purity of 86% to 99% and an
average particle size of 0.5 .mu.m to 5 .mu.m; 1% to 5% by weight of
fluorides selected from the group consisting of alkali metal fluorides and
cryolites of the formula:
M.sub.3 AlF.sub.6
where M is an alkali metal, as well as an agglomeration auxiliary agent in
amounts of 1% to 10% by weight.
2. The composite solid propellant of claim 1, wherein said agglomerate
contains said boron with a purity of 95% to 97% and an average particle
size of from 1 .mu.m to 3 .mu.m.
3. The composite solid propellant of claim 1, wherein said agglomerate
contains from 4% to 6% by weight of said agglomeration auxiliary agent.
4. The composite solid propellant of claim 1, wherein the agglomerate has a
particle size of between 200 .mu.m and 1,200 .mu.m.
5. The composite solid propellant of claim 1, wherein said agglomeration
auxiliary agent is soluble in an organic solvent and is selected from the
group consisting of polymethylmethacrylate, polystyrene, polyamides,
polyvinylpyrrolidone and polyester resins.
6. An agglomerated boron/fluoride perchlorate for use in a solid propellant
having a stable burning rate consisting essentially of from:
19% to 61% by weight of ammonium perchlorate with an average particle size
of 0.4 .mu.m to 10 .mu.m;
38% to 75% by weight of boron with a purity of 86% to 99% and an average
particle size of 0.5 .mu.m to 5 .mu.m;
1% to 5% by weight of fluorides selected from the group consisting of
alkali metal fluorides and cryolites of the alkali metals of the formula
Me.sub.3 AlF.sub.6 ;
where m is an alkali metal;
as well as an agglomeration auxiliary agent in amounts of from 1% to 10% by
weight.
7. A composite solid propellant with a stable burning rate consisting
essentially of:
40% to 80% by weight of an agglomerate of boron and ammonium perchlorate
consisting essentially of from:
19% to 61% by weight of ammonium perchlorate with an average particle size
of 0.4 .mu.m to 10 .mu.m;
38% to 75% by weight of boron with a purity of 86% to 99% and an average
particle size of 0.5 .mu.m to 5 .mu.m;
1% to 5% by weight of fluorides selected from the group consisting of
alkali metal fluorides and cryolites of the alkali metals of the formula
Me.sub.3 Alf.sub.6 ;
where M is an alkali metal;
as well as an agglomeration auxiliary agent in amounts of from 1% to 10% by
weight;
0% to 15% by weight of finely-divided, readily oxidizable metals;
10% to 40% by weight of a binder system selected from the group consisting
of telomeric polybutadiene and copolymers of butadiene and acrylonitrile,
both with terminal functional groups or functional groups distributed
statistically along the chain, which are hardened by means of
corresponding hardeners into rubber-elastic binders, and
0 to 5% by weight of burning rate moderators.
8. The composite solid propellant of claim 7, wherein said 10% to 40% by
weight of binder system consists of:
8% to 20% by weight of the total propellant of said polybutadiene or
copolymers of butadiene and acrylonitrile, with said functional groups,
0.5% to 5% by weight of the total propellant of said hardeners, and
0% to 20% by weight of the total propellant of plasticizers.
Description
BACKGROUND OF THE INVENTION
The present invention relates to a composite solid propellant with a stable
burning rate on the basis of ammonium perchlorate, telomeric binders with
terminal functional groups or functional groups statistically distributed
along the chain, which are hardened with corresponding hardeners into
rubber-elastic products, finely pulverized, readily oxidizable metals such
as magnesium, aluminum and zirconium and/or semi-metals such as boron and
silicon, and, optionally, inorganic fluorides, as well as plasticizers and
burning rate moderators.
The solid propellants which are used as energy sources for rockets usually
contain the oxygen required for combustion in the form of solid oxidizers.
In contrast thereto, in air-breathing boosters, oxygen from the air is
used with simultaneous employment of a strongly underbalanced composite
propellant. A strongly under-balanced composite propellant is one where
the amount of oxidizer is greatly insufficient to oxidize the
finely-pulverized metals. A significant increase in output or range is
thereby made possible, because in place of solid oxidizers additional fuel
can be carried. If this fuel partly consists of the metals magnesium,
aluminum or zirconium or the semi-metals boron or silicon, propellants are
obtained which, when burned with air, are far superior not only over the
conventional rocket propellants but also over hydrocarbon/air system such
as kerosene/air, for example.
A further increase in performance with equal dimensions of the rocket motor
can be achieved if the missile is capable of flying so-called
high/deep-profiles. The prerequisite for this is that the mass throughput
of the propellant is well regulatable, that is, that the propellant
possesses a high pressure exponent n. Here lies the disadvantage of the
heretofore employed underbalanced composite propellants, primarily when
finely divided metallic boron is used, which all exhibit a pressure
exponent that is unsuitable for regulating the mass throughput.
OBJECTS OF THE INVENTION
It is an object of the invention to provide a composite propellant for
air-breathing boosters, which can be well regulated with respect to its
burn properties.
Another object of the present invention is the obtaining of a composite
solid propellant with a stable burning rate comprising ammonium
perchlorate, a binder system of telomeric polybutadiene or copolymers of
butadiene and acrylonitrile with terminal functional groups or functional
groups distributed statistically along the chain, which are hardened by
means of corresponding hardeners into rubber-elastic binders, finely
pulverized, readily oxidizable metals and, optionally, inorganic
fluorides, plasticizers and burning rate moderators, wherein ammonium
perchlorate together with one or more of said finely pulverized metals, as
well as, optionally, said inorganic fluorides are present as an
agglomerate of larger particles having a particle size of between 100
.mu.m and 2,000 .mu.m.
A further object of the present invention is the production of an
agglomerated boron/ammonium perchlorate for use in a solid propellant
having a stable burning rate consisting essentially of from 19% to 61% by
weight of ammonium perchlorate with an average particle size of 0.4 to 10
.mu.m; from 38% to 75% by weight of boron with a purity of 86% to 99% and
an average particle size of 0.5 .mu.m to 5 .mu.m; from 0 to 6% by weight
of fluorides selected from the group consisting of alkali metal fluorides
and cryolites of the alkali metals of the formula
Me.sub.3 AlF.sub.6
where M is an alkali metal
as well as an agglomeration auxiliary agent in amounts of from 1% to 10% by
weight.
These and other objects of the present invention will become more apparent
as the description thereof proceeds.
DESCRIPTION OF THE INVENTION
The drawbacks of the prior art overcome and the above objects are achieved
according to the present invention if ammonium perchlorate together with
one or more of the finely powdered metals and/or semi-metals as well as,
optionally, the inorganic fluorides, as agglomerate of larger particles,
is contained in the composite solid propellant.
More particularly, therefore, the present invention relates to a composite
solid propellant with a stable burning rate comprising ammonium
perchlorate, a binder system of telomeric polybutadiene or copolymers of
butadiene and acrylonitrile with terminal functional groups or functional
groups distributed statistically along the chain, which are hardened by
means of corresponding hardeners into rubber-elastic binders, finely
pulverized, readily oxidizable metals and, optionally, inorganic
fluorides, plasticizers and burning rate moderators, wherein ammonium
perchlorate together with one or more of said finely pulverized metals, as
well as, optionally, said inorganic fluorides are present as an
agglomerate of larger particles having a particle size of between 100
.mu.m and 2,000 .mu.m.
Merely by agglomeration of the metal or semi-metal used as the principal
fuel with the oxidizer ammonium perchlorate, the pressure exponent can
surprisingly be increased four- to seven-fold over composite propellants
in which the components boron and ammonium perchlorate are added in the
same mixture ratio but separately. The quality of the boron/ammonium
perchlorate agglomerates (hereinafter referred to as Borap), the
preparation of which is described in the examples, has a decisive
significance for the utilization and the burn behavior. The indicated
compositions of Borap represents, of course, only one of many possible
compositions.
Of course, in addition to boron as a metal or ammonium perchlorate as an
oxidizer, other conventional metals and/or oxidizers may be agglomerated
in the same fashion.
A preferred embodiment of the invention provides that the agglomerate
consists of from 19% to 61% by weight of ammonium perchlorate with an
average particle size of 0.04 .mu.m to 10 .mu.m; from 38% to 75% by weight
of boron with a purity of 86% to 99%, preferably 95% to 97%, and an
average particle size of 0.5 .mu.m to 5 .mu.m; 0% to 6% by weight of
fluorides of the alkali metals and/or cryolites of the alkali metals of
the formula
Me.sub.3 AlF.sub.6
where M is an alkali metal
as well as an agglomeration auxiliary agent in amounts of 1% to 10% by
weight, preferably 4% to 6% by weight.
More particularly, the invention also resides in an agglomerated
boron/ammonium perchlorate for use in a solid propellant having a stable
burning rate consisting essentially of from 19% to 61% by weight of
ammonium perchlorate with an average particle size of 0.4 .mu.m to 10
.mu.m; from 38% to 75% by weight of boron with a purity of 86% to 99% and
an average particle size of 0.5 .mu.m to 5 .mu.m; from 0 to 6% by weight
of fluorides selected from the group consisting of alkali metal fluorides
and cryolites of the alkali metals of the formula
Me.sub.3 AlF.sub.6
where M is an alkali metal
as well as an agglomeration auxiliary agent in amounts of from 1% to 10% by
weight.
By virtue of the presence of inorganic fluorides of the first and second
main group of the periodic system or double fluorides with elements of the
third main group in concentrations of 1% to 5% by weight in the
agglomerate, a composite solid propellant with improved combustion effect
degrees is achieved. Preferred compounds, therefore, are the alkali metal
fluorides, such as LiF, NaF, Kf, the alkaline earth metal fluorides, such
as MGF.sub.2 CaF.sub.2, as well as the double fluorides NaBF.sub.4,
Li.sub.3 AlF.sub.6, Na.sub.3 AlF.sub.6, K.sub.3 AlF.sub.6.
This agglomerate, pursuant to a further characteristic has a particle size
between 100 .mu.m and 2,000 .mu.m, preferably between 200 .mu.m and 1,200
.mu.m. The agglomeration auxiliary agent consists, in accordance with an
advantageous embodiment, of organic solvent-soluble polymers, such as
polymethylmethacrylate, polystyrene, polyamides, polyvinylpyrrolidone or
polyester resins.
In accordance with a further embodiment of the invention, the composite
solid propellant has the following composition (in percent by weight):
Agglomerate 40% to 80%,
Metals 0% to 15%,
Binder system (binders, plasticizers auxiliaries) 10% to 40%,
Burning rate moderators 0% to 5%.
For increasing the output of air-breathing boosters, one or more light
metals, their alloys, semi-metals or metals are added to the propellant.
In most cases, the propellant contains several of the above-mentioned
components. These fuels, which are present in finely pulverized form with
a particle size between 0.5 .mu.m and 20 .mu.m are employed in amounts of
25% to 60%, preferably between 40% and 50%. Suitable light metals are, for
example, magnesium and aluminum. Suitable semi-metals are boron and
silicon, and a suitable metal is zirconium. As already mentioned, these
fuels are agglomerated with the ammonium perchlorate oxidizer and possibly
the inorganic fluorides into larger particles prior to use.
The oxidizers, which are employed in concentrations of 15% to 40%, consist
of alkali metal, ammonium and alkaline earth metal salts of nitric acid
and/or perchloric acid. For this purpose, the employment of ammonium
perchlorate and/or sodium nitrate proves to be particularly advantageous.
Other oxidizers which may be used within the scope of the invention are
the nitramines, RDX, HMX, nitroguanidine, guanidine nitrate,
triaminoguanidine nitrate, etc.
Preferred as binders are telomeric polymers, such as polybutadienes or
copolymers of butadiene and acrylonitrile, polyesters or polyethers with
functional groups. The functional groups may either be in terminal
position or statistically distributed along the chain. Typical examples
are terminal carboxyl-substituted polyesters and polybutadienes, terminal
hydroxyl-substituted polybutadienes and polyesters or copolymers of
butadiene and acrylic acid as well as terpolymers of butadiene/acrylic
acid/acrylonitrile. The last two are prepared by a complete or partial
hydrolysis of a butadiene-acrylonitrile copolymer.
If the functional group consists of a carboxyl group, these polymers can be
hardened with various aziridines, epoxides or amines. Polymers with
hydroxyl groups are hardened with aliphatic or aromatic di- or
polyisocyanates. Depending upon the reactivity of the isocyanate which is
used, hardening accelerators or hardening inhibitors are added.
In accordance with a further characteristic of the invention, the binder
system consists of 8% to 20% by weight of the total propellant of
polybutadiene or copolymers of butadiene and acrylonitrile with functional
groups; 0.5% to 5% by weight of the total propellant of hardener; and 0%
to 20% by weight of the total propellant of plasticizer.
The binder system may, of course, also be modified with components which do
not take part in the hardening process, such as aliphatic or aromatic
hydrocarbons and esters with a plasticizing function, process auxiliaries,
anti-oxidizing agents, etc.
The compounds which are conventional in propellant technology are used as
burning rate moderators. Among these are, for example, iron oxide, copper
chromite, copper oxide, manganese oxide, n-butylferrocene, organic iron
compounds, such as ferrocene, catocenes, etc. Depending upon the required
burning rate of the propellant, these moderators are added in the
concentration range of between 0% to 5%.
For further illustration of the invention, the following working examples
of the invention are given, which in no way limit the invention. (All
amounts in percent by weight.)
EXAMPLE A
Preparation of the Boron/Ammonium Perchlorate Agglomerate - Borap I
5 Parts by weight of polymethylmethacrylate were dissolved in 100 parts by
weight of methylene chloride. This solution was introduced into a
horizontal mixer with sigma-kneading blades, and 60 parts of metallic
boron with a particle size between 0.4 .mu.m and 5.0 .mu.m were added in
portions. After thorough mixing, 45 parts by weight of finely milled
ammonium perchlorate with an average particle size of about 3 .mu.m were
added to the formed mass. After the mass was homogenized by prolonged
mixing, the solvent was slowly drawn off at a pressure of 100 to 300 mm Hg
at room temperature while continuing the kneading. The kneaded mass is
progressively dried thereby and then disintegrates into a grainy
agglomerate. By means of screening, the agglomerate with the desired
particle size is then continuously removed, whereas the excessively large
particles are recycled into the kneading process. The agglomerate is then
dried at 80.degree. C. until it has a constant weight. This composition is
hereafter referred to as Borap I.
EXAMPLE B
Preparation of the Boron/Ammonium Perchlorate/Fluoride Agglomerate - Borap
II
A further increase in output of the composite solid propellant can be
achieved if additional inorganic fluorides are admixed with the Borap
ingredients before agglomeration. These admixtures have no additional
effect upon the increase of the pressure exponent, but they significantly
improve the combustion effect degree of the propellant. The following
example with the designation Borap II represents, of course, only one of
many possible compositions:
______________________________________
Composition of the Borap II agglomerate:
Parts by
Weight
______________________________________
60 Metallic boron
45 Ammonium perchlorate
4 Lithium fluoride
5 Polymethylmethacrylate
______________________________________
The preparation of the agglomerate is carried out in analogy to the
preparation of Borap I.
______________________________________
Percent by
Weight
______________________________________
42.0 Boron
8.0 Aluminum
25.0 Ammonium perchlorate
5.0 n-Butyl-ferrocene
13.0 Terminal carboxyl-substituted polybutadiene
6.5 Isodecyl pelargonate
0.5 Epoxide/aziridine hardener.
______________________________________
The components are admixed at 70.degree. C. into a pourable mass which,
after five days at 80.degree. C., hardens into a rubber-elastic mass. The
burn rate at 20.degree. C. and 30 bar is 11 mm/sec. The pressure exponent
of the propellant in the range between 30 and 150 bar is 0.10.
EXAMPLE 2
______________________________________
Percent by
Weight
______________________________________
68.0 Borap I
8.0 Aluminum
5.0 n-Butyl-ferrocene
13.0 Terminal carboxyl-substituted polybutadiene
5.5 Isodecyl pelargonate
0.5 Epoxide/aziridine hardener.
______________________________________
The compounding is carried out as in the preceding example, and one obtains
a rubber-elastic composite propellant with a burn rate of 4.5 mm/sec. at
20.degree. C. and 30 bar. The pressure exponent of the propellant in the
range between 30 and 150 bar is 0.48.
EXAMPLE 3
______________________________________
Percent by
Weight
______________________________________
68.0 Borap I
7.0 Aluminum
2.0 Nitroguanidine
2.0 n-Butyl-ferrocene
10.0 Terminal carboxyl-substituted polybutadiene
0.5 Epoxide/aziridine hardener
10.5 Naphthenic plasticizer.
______________________________________
The compounding is carried out as in Example 1. The burn rate of the
propellant at 20.degree. C. and 30 bar is 3 mm/sec. The pressure exponent
of the propellant in the range between 30 and 150 bar is 0.65.
EXAMPLE 4
Comparison
______________________________________
Percent by
Weight
______________________________________
45.0 Boron/LiF-agglomerate of 42% boron and
3% LiF (prepared by the process of Example A)
8.0 Aluminum
25.0 Ammonium perchlorate
1.0 n-Butyl-ferrocene
13.0 Terminal carboxyl-substituted polybutadiene
7.5 Isodecyl pelargonate
0.5 Epoxide/aziridine hardener.
______________________________________
The compound is carried out as in Example 1. The burn rate of the
propellant at 20.degree. C. and 30 bar is 12 mm/sec. The pressure exponent
of the propellant in the range between 30 and 150 bar is 0.09.
EXAMPLE 5
______________________________________
Percent by
Weight
______________________________________
70.0 Borap II
8.0 Aluminum
1.0 n-Butyl-ferrocene
13.0 Terminal carboxyl-substituted polybutadiene
7.5 Isodecyl pelargonate
0.5 Epoxide/aziridine hardener.
______________________________________
The compounding is carried out as in Example 1. The burn rate of the
propellant at 20.degree. C. and 30 bar is 3 mm/sec. The pressure exponent
of the propellant in the range between 30 and 150 bar is 0.57.
EXAMPLE 6
______________________________________
Percent by
Weight
______________________________________
67.0 Borap I
5.0 Magnesium
2.0 Nitro-guanidine
2.0 Lithium fluoride
2.0 n-Butyl-ferrocene
10.0 Terminal hydroxyl-substituted polybutadiene
9.2 Diisooctyl sebacate
2.8 Diisocyanate hardener.
______________________________________
The components are admixed at 50.degree. C. into a pourable mass which,
after eight days at 50.degree. C., hardens into a rubber-elastic mass. The
burn rate of the propellant at 20.degree. C. and 30 bar is 4 mm/sec. The
pressure exponent of the propellant in the range between 30 and 150 bar is
0.60.
EXAMPLE 7
______________________________________
Percent by
Weight
______________________________________
70.0 Borap II
5.0 Magnesium
2.0 Nitro-guanidine
2.0 n-Butyl-ferrocene
10.0 Terminal hydroxyl-substituted polybutadiene
8.2 Diisooctyl sebacate
2.8 Diisocyanate hardener.
______________________________________
The compounding is carried out as in Example 6. The burn rate of the
propellant at 20.degree. C. and 30 bar is 3 mm/sec. The pressure exponent
of the propellant in the range between 30 and 150 bar is 0.62.
The invention makes it possible to provide composite solid propellants with
elevated pressure exponent n and improved combustion effect degree.
The preceding specific embodiments are illustrative of the practice of the
invention. It is to be understood, however, that other expedients known to
those skilled in the art or disclosed herein, may be employed without
departing from the spirit of the invention or the scope of the appended
claims.
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